| 1. |
- Correa, D. F., et al.
(author)
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Geographic patterns of tree dispersal modes in Amazonia and their ecological correlates
- 2023
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In: Global Ecology and Biogeography. - : Wiley. - 1466-822X .- 1466-8238. ; 32:1, s. 49-69
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Journal article (peer-reviewed)abstract
- Aim To investigate the geographic patterns and ecological correlates in the geographic distribution of the most common tree dispersal modes in Amazonia (endozoochory, synzoochory, anemochory and hydrochory). We examined if the proportional abundance of these dispersal modes could be explained by the availability of dispersal agents (disperser-availability hypothesis) and/or the availability of resources for constructing zoochorous fruits (resource-availability hypothesis). Time period Tree-inventory plots established between 1934 and 2019. Major taxa studied Trees with a diameter at breast height (DBH) >= 9.55 cm. Location Amazonia, here defined as the lowland rain forests of the Amazon River basin and the Guiana Shield. Methods We assigned dispersal modes to a total of 5433 species and morphospecies within 1877 tree-inventory plots across terra-firme, seasonally flooded, and permanently flooded forests. We investigated geographic patterns in the proportional abundance of dispersal modes. We performed an abundance-weighted mean pairwise distance (MPD) test and fit generalized linear models (GLMs) to explain the geographic distribution of dispersal modes. Results Anemochory was significantly, positively associated with mean annual wind speed, and hydrochory was significantly higher in flooded forests. Dispersal modes did not consistently show significant associations with the availability of resources for constructing zoochorous fruits. A lower dissimilarity in dispersal modes, resulting from a higher dominance of endozoochory, occurred in terra-firme forests (excluding podzols) compared to flooded forests. Main conclusions The disperser-availability hypothesis was well supported for abiotic dispersal modes (anemochory and hydrochory). The availability of resources for constructing zoochorous fruits seems an unlikely explanation for the distribution of dispersal modes in Amazonia. The association between frugivores and the proportional abundance of zoochory requires further research, as tree recruitment not only depends on dispersal vectors but also on conditions that favour or limit seedling recruitment across forest types.
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| 2. |
- Meyer, E., et al.
(author)
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The state of the art in beyond 5G distributed massive multiple-input multiple-output communication system solutions
- 2022
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In: Open Research Europe. - : F1000 Research Ltd. - 2732-5121. ; 2
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Research review (peer-reviewed)abstract
- Beyond fifth generation (5G) communication systems aim towards data rates in the tera bits per second range, with improved and flexible coverage options, introducing many new technological challenges in the fields of network architecture, signal pro- cessing, and radio frequency front-ends. One option is to move towards cell-free, or distributed massive Multiple-Input Multiple-Output (MIMO) network architectures and highly integrated front-end solutions. This paper presents an outlook on be- yond 5G distributed massive MIMO communication systems, the signal processing, characterisation and simulation challenges, and an overview of the state of the art in millimetre wave antennas and electronics.
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| 3. |
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| 4. |
- ÖZEN, MUSTAFA, 1984, et al.
(author)
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A Generalized Combiner Synthesis Technique for Class-E Outphasing Transmitters
- 2017
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In: IEEE Transactions on Circuits and Systems I: Regular Papers. - : Institute of Electrical and Electronics Engineers (IEEE). - 1549-8328 .- 1558-0806. ; 64:5, s. 1126-1139
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Journal article (peer-reviewed)abstract
- In this paper, a generic combiner design technique is developed for class-E outphasing transmitters. The design procedure starts with calculation of the combiner network parameters that guarantee high efficiency switch mode operation of the PAs in each branch. Recently developed continuous class-E modes theory is then utilized to create an additional degree of freedom for calculation of the combiner network parameters. This additional degree of freedom along with duty cycle control provides an important possibility for achieving high average efficiency over a large bandwidth. A CMOS-GaN outphasing transmitter prototype is realized for experimental verification. The prototype provides drain efficiencies higher than 60% at 6 dB back-off across 750-1050 MHz band. Further, the peak output power remains nearly flat versus frequency, where the variation across the band is +/- 0.18 dB around 44 dBm.
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| 5. |
- ÖZEN, MUSTAFA, 1984, et al.
(author)
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High efficiency RF pulse width modulation with tunable load network class-E PA
- 2011
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In: 2011 IEEE 12th Annual Wireless and Microwave Technology Conference, WAMICON 2011. - 9781612840819
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Conference paper (peer-reviewed)abstract
- In this paper, a 10 W peak power 2 GHz highly efficient RF pulse width modulation (RF-PWM) based transmitter is presented. RF-PWM signals are generated with a dedicated 65 nm CMOS modulator and subsequently amplified with a GaN Class-E power amplifier (PA). The modulator use extended drain MOS (EDMOS) high voltage transistors to provide the required voltage swing to drive the GaN used as a switch. The imaginary load impedance of the Class-E is electronically tunable and is implemented with in-house high breakdown voltage SiC varactors. The tunable imaginary load impedance enables optimization of the Class-E versus the duty cycle (pulse width). The peak efficiency is therefore preserved over a wide range of output power levels. The measured drain efficiency of the Class-E output stage is above 70% over a 6.5 dB output power dynamic range. The overall transmitter efficiency is above 60% for the same dynamic range.
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| 6. |
- ÖZEN, MUSTAFA, 1984, et al.
(author)
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Wideband and efficient watt-level SiGe BiCMOS switching mode power amplifier using continuous class-E modes theory
- 2014
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In: Digest of Papers - IEEE Radio Frequency Integrated Circuits Symposium. - 1529-2517. - 9781479938629 ; , s. 243-246
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Conference paper (peer-reviewed)abstract
- In this paper, a generic, wide-band switch mode power amplifier (SMPA) design approach is developed based on the continuous class-E modes theory. A watt level, 1.3-2.2 GHz SiGe BiCMOS class-E SMPA is realized for experimental verification. The prototype provides collector efficiencies higher than 70% and output power levels higher than 29 dBm across 1.3-2.2 GHz band, fully confirming the validity of the proposed design approach.
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